Bellows or other flashing materials having one or more conveniently formed metal flanges attached thereto are widely used in the building construction industry. Specifically, Expand-O-Flash.RTM. expansion joint cover systems available from Manville Products Corporation utilize a bifurcated joint to permanently affix the metal flanges to the flexible bellows material. In use, each metal flange is fastened and adhered to portions of a roof construction leaving the bellows portion free to flex and thus compensate for any expansion and contraction of the building structure. This bellows construction can be made in accordance with U.S. Pats. No. 3,346,941, Re. No. 25733, and U.S. Pat. No. 3,468,285. Recently, however, it has been found that the use of more sophisticated bellows materials, specifically silicone rubber saturated glass fabric, has resulted in certain manufacturing difficulties. The adhesive material normally used to enhance the bifurcated joint tends to act as a lubricant prior to curing and sometimes causes the silicone bellows to slip out of the joint as the joint is being folded during the fabrication process. Slower production rates and a rise in rejects often result. One solution suggested by the prior art is to apply a contact adhesive to the adjoining metal and rubbery parts, permit the contact adhesive to partially or substantially cure and then bring the parts into clamping engagement. However, this solution further slows production rates.